boost problems

First off i want to thank everybody on these message boards i learn so much from u guys.... anyways heres my problem..... i am currently getting around 15 on vac and as soon as i hit boost it heisates stutters and i get none. kinda feels like its not getting fuel or spark not to sure i can also hear every so often like a back fire or a clog cat type of sound not sure how to explain the sound. it threw a code once yesterday as soon as i hit boost then when i went into vac the code went away wish i had a code reader but i dont. what should i start checking out first. fuel filter, spark any help... oh yea big question here ive called every local place including ford for a radiator fan motor noboby can get it and ford told me they stoped selling it and when they did it was 500.00 just for the motor where can i get what i need.

Well since you are from IL. I will help you out. 15 inches of vacume is low unless you have a large cam. It sounds like you have a vac leak and they are not easy to find. Some times its just a old hose that split or has fallen off. This is what I do. I use a 1 ft. length of vac or rad hose. put it in you ear and listen for hissing. As far as a motor for the fan I have a used one for sale.
$45.00 + shipping but will need to know what year we are talking about first. there ars so many things that could be causing your problems but getting your vac up would be first on my list. after that you could take it some where and have them check just for codes and repair your self. Let me know what year your car is tho.
Mark Oh by the way 18-20 on vac is nomal. all mine sit on 20